class Phone {
  
  @Deprecated("message")
  open() {
    print("开机");
  }
  close() {
    print("关机");
  }

}

class IPhone15 extends Phone {

  @override
  open() {
    print("IPhone15 开机");
  }

  @override
  close() {
    print("IPhone15 关机");
  }
}

void main() {
  Phone phone = new Phone();
  phone.open();
  phone = new IPhone15();
  phone.open();

}